Mast rail
The mast rail or mast slide rail is the rail attached to the aft (rear) side of the ship's mast in which the mainsail is moored. On sailing right are to luff attached to the luff keep on track.
Mast rails can take various forms. The traditional and still widespread one is a notch that is adapted to the diameter of the mast, into which the plastic mast slides are inserted - very similar to the T-rail of a curtain . The advantages are the simple construction, the cheap associated mast slider and the relatively close fit of the sail luff on the mast. The latter is beneficial for aerodynamics. The resulting relatively high friction is a disadvantage. As an alternative, especially on larger boats, a profile rail is welded onto the mast on which sledges fitted with ball-bearing wheels are moved. This design has a significantly lower frictional resistance, but is also heavier and more expensive.
In order to attach or detach the mainsail - which usually only happens once a season - the notch is widened just above the Lümmel fitting so that the slide can be inserted there. The hole can then be closed differently depending on the construction, for example with a mast slide stopper in the form of a bolt.
The mast rail must not be confused with the mast track . This is a (very short) rail used in particular on regatta boats on which the mast is placed and can be moved in its position for trimming purposes.